From: Peter Lieven <pl@kamp.de>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Orit Wasserman <owasserm@redhat.com>,
quintela@redhat.com, qemu-devel@nongnu.org,
Stefan Hajnoczi <stefanha@gmail.com>
Subject: Re: [Qemu-devel] [PATCHv4 0/9] buffer_is_zero / migration optimizations
Date: Mon, 25 Mar 2013 12:26:47 +0100 [thread overview]
Message-ID: <CC5AC377-A8B1-4FD2-B249-8A27476D1ED6@kamp.de> (raw)
In-Reply-To: <1328150503.13028038.1364208799172.JavaMail.root@redhat.com>
Am 25.03.2013 um 11:53 schrieb Paolo Bonzini <pbonzini@redhat.com>:
>> ubuntu 12.04 LTS 64-bit desktop with 1G memory shortly after boot:
>> histogram: 31.7% 32.9% [...] 36.4% 100.0%
>>
>> ---
>>
>> opensuse 11.1 64-bit with 24GB ram (busy server)
>> histogram: 97.5% 97.9% [...] 99.5% 100.0%
>>
>> ---
>>
>> windows server 2008 R2 with 8G ram running for 3 days:
>> histogram: 20.9% 21.3% [...] 22.5% 100.0%
>>
>> ---
>>
>> windows XP guest with 1G Ram running for approx. 1 hours
>> histogram: 25.6% [...] 35.8% 100.0%
>
> Doesn't this suggest checking the first _and the last_ word,
> and using the vectorized loop if none is zero?
Maybe I should have explained the output more detailed. The percentages are added. 35.8% in the second last column means that 35.8% have a return
value that is less than TARGET_PAGE_SIZE. This was meant to illustrate at how many 64-bit chunks you have to look to grab a certain
percentage of non-zero pages.
25.6% 26.1% 34.0% 34.1% 34.2% 34.3% 34.3% 34.4% 34.4% 34.4% 34.5% 34.5% 34.5% [...] 35.8% 100%
Looking e.g. at the third value it means that looking at the first three 64-bit chunks it will catch 34.0% of all pages.
It turns out that the non-zeroness of a page can be detected looking at the first 256 or so bits and only a low
percentage turns out to be non-zero at a later position. So after having checked the first chunks one by one
there is no big penalty looking at the remaining chunks with the vectorized loop.
Here is the distribution of return values for the Windows XP example:
25.62% 0.49% 7.86% 0.12% 0.15% 0.05% 0.05% 0.04% 0.05% 0.02% 0.03% 0.02% 0.03% 0.02% 0.02% 0.01% 0.03% 0.02% 0.01% 0.02% 0.02% 0.01% 0.02% 0.01% 0.01% 0.01% 0.01% 0.01% 0.02% 0.00% 0.01% 0.02% 0.03% 0.01% 0.01% 0.01% 0.01% 0.01% 0.01% 0.00% 0.00% 0.01% 0.07% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.01% 0.02% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.02% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.03% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.02% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.02% 0.00% 0.00% 0.02% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 64.23%
The last value is the percentage of return value of TARGET_PAGE_SIZE meaning the page is all zero.
Peter
next prev parent reply other threads:[~2013-03-25 11:26 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-22 12:46 [Qemu-devel] [PATCHv4 0/9] buffer_is_zero / migration optimizations Peter Lieven
2013-03-22 12:46 ` [Qemu-devel] [PATCHv4 1/9] move vector definitions to qemu-common.h Peter Lieven
2013-03-25 8:35 ` Orit Wasserman
2013-03-22 12:46 ` [Qemu-devel] [PATCHv4 2/9] cutils: add a function to find non-zero content in a buffer Peter Lieven
2013-03-22 19:37 ` Eric Blake
2013-03-22 20:03 ` Peter Lieven
2013-03-22 20:22 ` [Qemu-devel] indentation hints [was: [PATCHv4 2/9] cutils: add a function to find non-zero content in a buffer] Eric Blake
2013-03-23 11:18 ` Peter Maydell
2013-03-25 8:53 ` [Qemu-devel] [PATCHv4 2/9] cutils: add a function to find non-zero content in a buffer Orit Wasserman
2013-03-25 8:56 ` Peter Lieven
2013-03-25 9:26 ` Orit Wasserman
2013-03-25 9:42 ` Paolo Bonzini
2013-03-25 10:03 ` Orit Wasserman
2013-03-22 12:46 ` [Qemu-devel] [PATCHv4 3/9] buffer_is_zero: use vector optimizations if possible Peter Lieven
2013-03-25 8:53 ` Orit Wasserman
2013-03-22 12:46 ` [Qemu-devel] [PATCHv4 4/9] bitops: use vector algorithm to optimize find_next_bit() Peter Lieven
2013-03-25 9:04 ` Orit Wasserman
2013-03-22 12:46 ` [Qemu-devel] [PATCHv4 5/9] migration: search for zero instead of dup pages Peter Lieven
2013-03-22 19:49 ` Eric Blake
2013-03-22 20:02 ` Peter Lieven
2013-03-25 9:30 ` Orit Wasserman
2013-03-22 12:46 ` [Qemu-devel] [PATCHv4 6/9] migration: add an indicator for bulk state of ram migration Peter Lieven
2013-03-25 9:32 ` Orit Wasserman
2013-03-22 12:46 ` [Qemu-devel] [PATCHv4 7/9] migration: do not sent zero pages in bulk stage Peter Lieven
2013-03-22 20:13 ` Eric Blake
2013-03-25 9:44 ` Orit Wasserman
2013-03-22 12:46 ` [Qemu-devel] [PATCHv4 8/9] migration: do not search dirty " Peter Lieven
2013-03-25 10:05 ` Orit Wasserman
2013-03-22 12:46 ` [Qemu-devel] [PATCHv4 9/9] migration: use XBZRLE only after " Peter Lieven
2013-03-25 10:16 ` Orit Wasserman
2013-03-22 17:25 ` [Qemu-devel] [PATCHv4 0/9] buffer_is_zero / migration optimizations Paolo Bonzini
2013-03-22 19:20 ` Peter Lieven
2013-03-22 21:24 ` Paolo Bonzini
2013-03-23 7:34 ` Peter Lieven
2013-03-25 10:17 ` Peter Lieven
2013-03-25 10:53 ` Paolo Bonzini
2013-03-25 11:26 ` Peter Lieven [this message]
2013-03-25 13:02 ` Paolo Bonzini
2013-03-25 13:23 ` Peter Lieven
2013-03-25 13:32 ` Peter Lieven
2013-03-25 14:34 ` Paolo Bonzini
2013-03-25 21:37 ` Peter Lieven
2013-03-26 8:14 ` Peter Lieven
2013-03-26 9:20 ` Paolo Bonzini
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